Thin film speaker apparatus for use in a thin film video monitor device

ABSTRACT

A speaker system for use in a thin film video monitor apparatus is disclosed. The video monitor apparatus includes a thin film video display panel as well as a stiffening panel adjacent to the thin film video display panel. Next, a plurality of piezo speaker transducers are attached to one of the sides of the stiffening panel. The stiffening panel typically is composed of a material such as aluminum honeycomb sheets or a polycarbonate sheet. Other materials for use as the stiffener may include magnesium shells or ABS plastic. The speakers are defined so that a first sound channel and a second sound channel are provided, and these sound channels can define a left and right channel for proper stereo imaging. Between the video monitor and the stiffening panel is located an electromagnetic interference (EMI) shield. Further, a transmission line is provided to connect a first piezo transducer to a second piezo transducer in such a way so that frequency overlap can occur between the two transducers based upon the transmission line distance defined for the first piezo transducer and for the second piezo transducer. Further, the transmission line may have the same distance between both speakers where frequency overlap is not a concern. The stiffening panel is provided to increase the mobile energy in the lower frequencies during operation.

RELATED APPLICATIONS

This application is related to co-pending application Ser. No.08/810,430, filed on Mar. 4, 1997, Attorney Docket No. COM693/4-1234,entitled "MULTIPLE CHANNEL SPEAKER SYSTEM FOR A PORTABLE COMPUTER," andincorporated by reference herein.

THE FIELD OF THE INVENTION

The present invention relates generally to audio systems implemented incomputer systems and, more particularly, an audio sound system for usein a portable computer. More particularly still, the present inventionrelates to an audio system using piezo transducers to increase audiofidelity in portable laptop-type computers having a limited form factorfor optimizing audio sound.

PRIOR ART

Multimedia computers have now arrived in laptop computer systems. Thesemultimedia computer systems typically have color LCD display panels, CDROM drives, and audio speaker systems. Before the arrival of multimediaintegrated systems in laptop computers, most laptop computers had merelya single audio source or audio output means that had very limiteddynamic range. Further, a sound card capable of reproducing true highfidelity sound was typically lacking in most laptop computers. With theadvent of multimedia systems, these improved sound card systems havebeen integrated into laptop computers, as well as the addition of stereohigh fidelity sound.

Unfortunately, laptop computers have a limited form factor, typicallythe size of a notebook or a single sheet of paper roughly conforming tothe dimensions of 81/2×11 inches, thus a limited surface area or spaceis available for adding speakers. Currently, the LCD display panels areof such a size that room is still afforded on the monitor panel of thelaptop to incorporate two small speakers in either comer. As the LCDtechnology enlarges the size of the monitors, the full face on theinside panel of the monitor display will be completely filled with themonitor itself. This will leave no room for speakers at on the panelfacing the user. Additionally, the location of the speakers in mostlaptops is not ideal with respect to optimizing the frequency responseand dynamic range, as well as the spacial separation of the sound. Thespeakers are placed relatively close within one foot of each other inthe corners of the monitor display lid.

One approach has been to switch from speaker elements that use a movingdiaphragm as found in conventional speakers to piezo speakers.

Piezo speakers typically are thin polymer sheets (PVDF) or ceramic disksthat can be mounted virtually anywhere as compared to diaphragm-typeconventional speakers that must be given a set room for the magnet andvoice rail excursion requirements. Further, with the thinness of thepiezo speakers, the form factor of the top on the laptop computer can besubstantially dedicated to the display screen itself, where the piezospeakers can be mounted somewhere out of view.

Unfortunately, even with the advent of piezo speakers in laptopcomputers, other problems are inherent. These problems include thedistortion and lack of high fidelity that occur with piezo speakers.Typically, piezo speakers have limited low end due to excursionlimitations, but are most adequate at achieving high-end frequencyresponse. It is this low-end frequency response as well as the acousticsof the laptop cover that are still challenges in implementing piezospeakers in laptop computers. For this reason, there is a strong need toimprove the high fidelity sound system in laptop computers by way ofimproving the performance of either piezo speakers or by providing analternative speaker design that conforms to the expanding screen sizelocated in the cover of the laptop and yet provides full rich sound in amultimedia environment.

SUMMARY OF THE INVENTION

According to the present invention, a speaker system for use in a thinfilm video monitor apparatus is disclosed. The video monitor apparatusincludes a thin film video display panel as well as a stiffening paneladjacent to the thin film video display panel. Next, a plurality ofpiezo speaker transducers are attached to one of the sides of thestiffening panel. The stiffening panel typically is composed of amaterial such as aluminum honeycomb sheets or a polycarbonate sheet.Other materials for use as the stiffener may include magnesium shells orABS plastic. The speakers are defined so that a first sound channel anda second sound channel are provided, and these sound channels can definea left and right channel for proper stereo imaging. Between the videomonitor and the stiffening panel is located an electromagneticinterference (EMI) shield. Further, a transmission line is provided toconnect a first piezo transducer to a second piezo transducer in such away so that frequency overlap can occur between the two transducersbased upon the transmission line distance defined for the first piezotransducer and for the second piezo transducer. Further, thetransmission line may have the same distance between both speakers wherefrequency overlap is not a concern. The stiffening panel is provided toincrease the mobile energy in the lower frequencies during operation.

In another embodiment, the thin film speaker apparatus is designed foruse in a laptop computer, and in either case the thin film speakers canfurther include a plurality of sound equalizers, one equalizer attachedto each piezo transducer. The sound equalizers allow each transducer tobe optimized for sound playback. Additionally, a time delayer can alsobe added to provide enhanced frequency overlap and other soundmanipulations as desired by the designer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a laptop computer having an audio speaker systemincorporated therein according to the present invention.

FIG. 2 depicts an open view of the shell top of the laptop computer inFIG. 1.

FIG. 3 depicts a graph showing how two speakers are connected with atransmission line having different lengths so as to provide frequencyoverlap.

FIG. 4 depicts a multiple channel embodiment of the sound systemaccording to the present invention.

FIG. 5 illustrates in block diagram form the use of a time delay elementand sound equalizer for optimizing sound in the audio sound system.

FIG. 6 depicts, in a cut-away perspective view, the aluminum honeycombsupport used in the top shell of the computer in FIG. 2.

FIG. 7 depicts the placement of the speakers in a rest support in acomputer.

FIG. 8 depicts the speakers placed in an alternate embodiment such as adesktop lamp fixture.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Illustrated now in FIG. 1 is a multimedia laptop computer 10 accordingto the present invention. The laptop computer 10 is a multimedia-typecomputer having a monitor display panel 12, a keyboard 14, a pointingdevice 16, disk storage means 18, and audio speakers 20. The diskstorage means 18 may include various types of disk storage technologysuch as a floppy disk drive, a hard disk drive, or a compact disk readonly memory (CD-ROM) drive, or other type writeable or erasable storagedevices typically known to those skilled in the art. Keyboard 14provides data input for the user as does pointing device 18. Further,video monitor display panel 12 is of the type that fill substantiallythe shell top 22 of laptop computer 10. The keyboard 14, pointing device16, and storage device normally are located in the shell bottom 24 ofcomputer 10.

Within computer 10 there are other various devices for operation. Thesedevices include a central processing unit, such as those typicallyprovided by the Intel family of personal computing microprocessors suchas the Pentium chip or the IBM Power PC chip also found in laptopcomputers. Additionally, short-term memory that is fast and responsiveto the same operating speed as the CPU are also included as is a massstorage unit, typically the hard disk drive 18 previously describedabove. Additional control elements and peripherals are incorporated inthe computer, and the fundamental construction of a laptop computer doesnot diverge substantially from those typically well-known to thoseskilled in the art. Their location is in shell bottom 24.

Shown in greater detail in FIG. 2 is the audio output systemincorporated in the shell top 22 laptop computer 10. The audio outputsystem includes the piezo speakers 20 thus depicted. FIG. 2 illustratesan open view of the shell top 24, which doubles as the lid on the laptopcomputer 10, in such a manner as to locate the piezo speakers ideally ina form factor consistent with the ever enlarging monitor display panel12 of computer 10. The speakers 20 are located in such a manner as toprovide sound imaging away from the laptop operator during operation.This is so because in the functioning mode, the laptop cover is open forthe user to view screen 12. In this mode, the top of the laptop computerfaces away from the user and thus allows the speakers to direct thesound away from the user. Increase spatial imaging is now possible withthe sound directed away from the user and then reflected back from thewalls or furniture, or both, surrounding the user. Moreover, in apresentation environment, the speakers that project away from the userare ideally situated to project towards the audience during thepresentation.

Although the speakers have been shown to be implemented in the back ofthe LCD panel, it is understood that the piezo speakers may be mountedin other places besides the monitor housing. For example, the piezos maybe mounted on the LCD screen itself or on the palm rests in the baseunit. Further, wings may also be attached to the laptop computer in sucha way as to provide mounting for the piezo speakers and can be thinenough that they would be easily transported with the user forattachment and operation.

When the speakers 20 are mounted in the palm rests, as illustrated inFIG. 8, the sound transmits almost transparently through a user's hands.The placement of speakers 20 in the palm rests is optional, but doeshave unintended benefits since the sound travels through the user'shands with minimal distortion or diminution in volume as compared todiaphragm speakers.

In attaching the speakers to the back of the shell top 22, they mayactually be designed into the top cover in such a way as to bemanufactured in a single step when the cover itself is manufactured.Additionally, lead wires from the audio output source, typically mountedon the circuit board within the main unit of the laptop computer 10typically located under the keyboard section, are attached with flexiblecable wired in the panels.

A transmission line 26 is provided to enhance the richness and acousticresponse of piezo speakers 20. The transmission line illustrated in FIG.2 allows for piezo speakers 20 in the back of the shell top 22 of laptopcomputer 10 to be ported to port 27 in the front of the monitor panel.This transmission line provides a simple single-sided transmission linelabyrinth that is suitable for the thin form factor provided in themonitor panel. Since there is little depth allowed in the monitor panel,the transmission line is most suitable as boundary areas decrease. Thetransmission line can be tuned to the same of different frequencydepending on the desires of the manufacturer or the end user.

A transmission line is useful in that it allows for a pair of speakersto fill in a frequency response range that typically misses particularfrequencies due to the lack of excursion otherwise capable. This is soin that the transmission line is adjusted so that there is set at aratio of one length to another length between the two speakers so that afine tuning occurs to overlap the frequency responses between the twospeakers in an attempt to fill in the gaps. This is illustrated in thegraph shown in FIG. 3A. In FIG. 3A, the input signal is skewed over acertain frequency range so as to fill in the gaps and the responsesshown in FIG. 3B where an additional filter may be employed to cut offany part of the wave that cannot be skewed substantially in a usablemanner. Where two speakers are now linked via the transmission line, anincreased sound image is generated than would otherwise be possiblewithout the use of the transmission line.

Furthermore, an improved sound processing arrangement has beenimplemented and is known as AC3, developed by Dolby Labs, which providesfor five-channel prologic sound synthesizing. In this AC3 system, fiveseparate channels may be used, which gives the audio system designer theability to fine tune the sound system in a manner where the soundoverlap or cancelization can optimize the actual sound heard and enjoyedby the system user. For example, one embodiment is depicted in FIG. 4that includes a first or left channel 52, a second or right channel 54,and a center or third channel 56. Additionally, a bass channel 58 may beprovided by using two separate channels, each driving the same bassresponse frequency in a bass speaker 60. It has been shown in thisembodiment to use five separate channels. The system may have as few asone channel but ideally would have at least three channels, being onefor the left signal, one for the right signal and one for the bassresponse. Additionally, other channel configurations may be implementedby the designer according to the needs of the system.

Each channel is adjusted for optimal polar pattern placement, which canuse multiple piezo transducers. In this example, each of the leftchannel, center channel, and right channels include three discrete piezospeakers. All these speakers are placed on the back of the laptopcomputer monitor panel. Furthermore, a dedicated sound equalizer 62,shown in FIG. 5, is provided for each channel. Typically, a time delay64 and sound equalization 62 is provided and is illustrated in the blockdiagram of FIG. 5. In FIG. 5, a lower right channel is provided soundequalization and then time delay, where the lower left channel then alsois provided sound equalization and time delay and then are outputted totheir various actual speaker units or piezo transducers. Additionally,the center speaker 56 also receives sound equalization with a timedelay, as does the left and the right bass speakers 58.

Furthermore, the piezo speaker transducers are customized and optimizedfor the acoustic image desired to be achieved and would be well withinthe skilled artisan's ability to match such optimization once thedesired sound acoustic image is established.

The monitor lid top shell 22 of FIG. 2 further includes an aluminumhoneycomb support 70, which is illustrated in cut away perspective viewin FIG. 6, that provides two functions. The aluminum honeycomb supportfirst provides a stiffening of the plastic shell in which the LCDmonitor is mounted. Secondly, the aluminum honeycomb sheet improvessound reproduction by lowering the natural frequency response (f₀) toincrease the N_(rad) efficiency and to optimize power efficiency fromthe piezo speaker to the shell top 22. The thickness of support 70 isbetween 0.125"-0.250" Further provided in the monitor shell top 22 iselectromagnetic interference (EMI) shield 72 displaced between thespeakers 20 and the LCD monitor panel 18. Further provided is a plasticenclosure 74 over the entire assembly to top shell 22.

With the aluminum honeycomb support 70, piezo speakers 20 may be mountedon either side, and in some embodiments may be mounted opposite eachother on different sides. Other types of support 70 may be constructedfrom polycarbonate or ABS plastic, or even magnesium.

Afterwards, the piezo transducers 20 may also be tuned to be out ofphase so as to increase banding to achieve greater channel separation.Next, the boundary conditions are examined due to the LCD/panel air gapsand then appropriate dampening and stiffening are then performed. Next,boundary conditions are then investigated to determine whether the panelattachment points cause undesired effects so that additional dampeningand reaction forces can be counteracted to optimize the spatial soundand quality of the sound volume. This achieve by a mechanical dampeningof stiffener panel support 70 or modifies the relative phases betweenthe drivers. Further, the modal energy is optimized in the lowerfrequencies by preserving modal density and increasing radiationefficiency through the use of stiffening support 70.

Although it has been described for use in a laptop computer, thetransmission line system thus illustrated would also be applicable toany environment where a thin form factor, ie., lacking depth, would beideal for the use of piezo speaker transducers. This would be suitablewhere a simple LCD monitor has been designed for desk-top use andcumbersome speakers would be inappropriate for placement on the desk topitself. The speaker design would be added to such an LCD desk-topmonitor and provide the same quality of sound when customized to thatparticular monitor enclosure used with the LCD monitor. This preservesvaluable desk-top space otherwise required by the placement of speakers.

Additionally, where any flat surface is available that is typicallyassociated with a user, for example, a desk-top lamp fixture shown inFIG. 7, the piezo electric speakers can be mounted on the top surface ofthe sound fixture to provide sound directed towards the user or off aflat surface for improved sound separation.

Thus has been described a novel sound system for use ins limitedform-factor environments, such as laptop computers, that uses multiplechannels, transmission lines, and custom tuning. The foregoingdisclosure and description of the invention are illustrative andexplanatory thereof, and various changes in the size, shape, materials,components, circuit elements, wiring connections and contacts, as wellas the details of the illustrated design and construction and method ofoperation may be made without departing from the spirit of theinvention.

What is claimed:
 1. A thin film video monitor apparatus comprising:athin film video display panel; a stiffening panel, placed adjacent saidthin film video display panel; a plurality of piezo transducers,attached to at least a first side of said stiffening panel, and anacoustic labyrinth transmission line for connecting a first piezotransducer and a second piezo transducer selected from said plurality ofpiezo transducers to provide a first distance for said first piezotransducer and a second distance for said second piezo transducer and toprovide frequency overlap between said two piezo transducers.
 2. A thinfilm video monitor apparatus according to claim 1 wherein saidstiffening panel comprises an aluminum honeycomb sheet.
 3. A thin filmvideo monitor apparatus according to claim 1 wherein said stiffeningpanel comprises a polycarbonate sheet.
 4. A thin film video monitorapparatus according to claim 1 wherein said plurality of piezotransducers include at least a first sound channel and a second soundchannel corresponding to the first piezo transducer and the second piezotransducer, respectively.
 5. A thin film video monitor apparatusaccording to claim 1 further comprising an electromagnetic interference(EMI) shield placed adjacent a rear portion of said thin film videodisplay panel and said stiffening panel.
 6. A thin film video monitorapparatus according to claim 1 further comprising an air gap betweensaid thin film video display panel and said stiffening panel.
 7. A thinfilm video monitor apparatus according to claim 1 wherein said pluralityof said piezo transducers further comprises a low-frequency channelspeaker transducer and is mounted to said stiffening panel so as topreserve the modal energy in said lower frequencies.
 8. A thin filmspeaker apparatus comprising:a thin film video display panel; astiffening panel, placed adjacent said thin film video display panel; aplurality of piezo transducers, attached to at least a first side ofsaid stiffening panel; and an acoustic labyrinth transmission line forconnecting a first piezo transducer and a second piezo transducerselected from said plurality of piezo transducers to provide a firstdistance for said first piezo transducer and a second distance for saidsecond piezo transducer and to provide frequency overlap between saidtwo piezo transducers.
 9. A thin film speaker apparatus according toclaim 8 wherein said stiffening panel comprises an aluminum honeycombsheet.
 10. A thin film speaker apparatus according to claim 8 whereinsaid stiffening panel comprises a polycarbonate sheet.
 11. A thin filmspeaker apparatus according to claim 8 wherein said plurality of piezotransducers include at least a first sound channel and a second soundchannel corresponding to the first piezo transducer and the second piezotransducer, respectively.
 12. A thin film speaker apparatus according toclaim 8 further comprising an electromagnetic interference (EMI) shieldplaced adjacent a rear portion of said thin film video display panel andsaid stiffening panel.
 13. A thin film speaker apparatus according toclaim 8 further comprising a plurality of sound equalizers, each coupledto a respective one of said plurality of piezo transducers.
 14. A thinfilm speaker apparatus according to claim 8 further comprising an airgap between said thin film video display panel and said stiffeningpanel.
 15. A thin film speaker apparatus according to claim 8 whereinsaid thin film video display is coupled to a portable computer unit,thereby forming a portable computer.
 16. An audio speaker system for usein a computer component having a limited form factor, said audio speakersystem comprising:a first piezo speaker transducer mounted on a firstposition of said computer component; a second piezo speaker transducermounted to a second location of said computer component; a first andsecond sound equalizer, each coupled to said first and second speakertransducer, respectively; an acoustic labyrinth transmission lineconnecting said first piezo speaker transducer to said second piezospeaker transducer and having a first distance for said first piezospeaker transducer and a second distance for said second piezo speakertransducer so as to overlap frequencies between said first and secondpiezo speaker transducers.
 17. A laptop computer according to claim 16further comprising:a first channel corresponding to said first piezospeaker transducer; and a second channel corresponding to said secondpiezo speaker transducer.
 18. A laptop computer according to claim 16wherein said transmission line further comprises a sound chamber.
 19. Alaptop computer according to claim 17 wherein said first channelcorresponds to a left channel, and said second channel corresponds to aright channel for providing stereo imaging of said sound emanating fromsaid first piezo speaker transducer and said second piezo speakertransducer.
 20. A laptop computer according to claim 16 wherein saidaudio speaker system includes up to five separate channels and conformsto the AC-3 sound processing system.
 21. A laptop computer according toclaim 16 wherein said audio speaker system provides for said speakertransducers to be mounted in such a fashion as to direct the soundpressure away from a user when said computer is in use.
 22. The laptopcomputer according to claim 16 wherein said transmission line is asingle-sided labyrinth.
 23. A laptop computer according to claim 16further comprising a time delayer, coupled to one of said pluralitysound equalizers.